A halogen-containing resin is unstable with regard to heat or light. Therefore, it is necessary to incorporate a thermal stabilizer before heating and melt-molding. A lead compound, an organotin compound, a Cd/Ba-containing complex metal soap, a Ba/Zn-containing complex metal soap, a Ca/Zn-containing complex metal soap and a hydrotalcite have been used as the thermal stabilizer. However, the use of a Cd or Pb-containing stabilizer, which is toxic, has been gradually prohibited. In particular, since the lead compound is economical and exhibit high performance, it is used in large quantities. Accordingly, it is important to develop a substitute stabilizer.
A hydrotalcite is nontoxic and also excellent in thermal stability. However, it has crystal water so that a defect is that foaming occurs when the amount of the hydrotalcite to be incorporated is large. On the other hand, calcium hydroxide has no crystal water so that it is free from foaming and also excellent in thermal stability. However, when the amount of the calcium hydroxide to be incorporated is increased, torque increases during processing of a resin in some cases. Further, another defect thereof is that it gives strong coloration.